Apparatus for cleaning wells



Nov. 9, 1937. J. GRANT APPARATUS FOR CLEANING WELLS 3 sheets-sheet 1Filed July 20, 1935 m C f N VII Nov. 9, 1937. J. GRANT 2,098,494

APPARATUS FOR CLEANING WELLS Filed July 20, 1955 5 Sheets-Sheet 2 f\\\||I.Cf Il T, m m, @$0 n Nov. 9, 1937. J. GRANT 2,098,494

APPARATUS FOR CLEANING WELLS Filed July 20, 1935 3 Sheets-Sheet 3Patented Nov. 9, 1937 UNITED STATES PATENT OFFICE 20 Claim!- Thisinvention deals generally with apparatus which operates by the suddenrelease of-well pressureinto a low pressure or charge receiving chamberlowered into the well, to induce into said chamber a flow of well fluidcarrying with it solid particles or bodies which it is desired to removefrom the well or from the well pipe perforations. Apparatus oi thisgeneral type, and to all of which the invention is broadly applicable,includes suction-type fishing tools. bailers, and well cleaners forremoving from the well screen perforations clogging particles, sand orother obstructing bodies.

The type of apparatus referred to abovevmay l5 lbe described generallyas comprising a normally closed low pressure chamber contained within atubular body portion of the apparatus or within the pipe on which theapparatus is suspended, and which is lowered, while closed, to the depthat which the operation is to be carried out. The low pressure chamberclosure usually consists of a valve or member, such as a frangible disk.adapted to be opened or broken, as the case may be, to admit a charge ofwell fluid to the chamber.

The present invention relates particularly to apparatus of this typeutilizing a frangible member as the charge receiving chamber closure.

Heretoiore, in such apparatus using a frangible member or disk as theclosure, the closure opening means has consisted of a breaking memberprojected against the disk, or against which the disk is impacted. Inspite of provisions made for bringing the disk and breaking memberforcibly into engagement, it is frequently found that due to variousconditions existing in the well, it is diillcult to break the disk. Infact, where the apparatus is not adapted to deliver repeated blowsagainst the disk, it becomes necessary where the disk remains unbrokenafter one operation of the breaking member, to withdrawn the apparatusfrom the well, reset the disk breaking mechanism, and repeat theoperation.

One of the primary objects of the invention is to provide a breakingmeans` for the frangible closure that will insure complete shattering ofthe latter in a single operation. The invention is characterized frompast practice in that it utilizes an explosive for breaking the closureto place the charge receiving chamber into communication with the well.As will hereinafter appear, the invention is adaptable to variousstructural iorrns with respect to the particular way in which theexplosive is used to rupture the disk. Preferably, the explosive isapplied directly to the disk, and red by suitable means such as anelectric current or by a firing pin projected against the explosive Onthe other hand if desired, the explosive may be located extraneous tothe disk and utilized indirectly to supply the disk breaking force, byiiring a projectile against the disk.

'I'he above mentioned and various additional features and objects of theinvention, as well as the details o! certain typical and illustrative'forms, will be more fully understood from the description to follow.Throughout the descrip- 1G tion reference is made to the accompanyingdrawings, in which:

Fig. 1-is a longitudinal section showing theupper portion of the wellcleaning apparatus below the charge receiving chamber;

Fig. 2 is a downward continuation of Fig. r1 illustrating the lowerportion of the apparatus;

Fig. 3 is a sectional view showing the body portion containing thecharge receiving chamber;

Figs. 4 and 5 are sectional views similar to Figs. 2( 1 and 2,respectively, but showing the parts in changed position aiter the chargereceiving chamber has been opened; A

Fig. 6 is an enlarged fragmentary section on line 6-6 of Fig. 1, showingthe switch mechanism;

Figs. l and 8 are sections taken on lines 1--1 and 8-8 of Figs. 1 and 2,respectively;

Fig. 9 is a fragmentary section showing a variational form of diskbreaking mechanism; and

Fig. 10 is a view similar to Fig. 9 showing a furv ther variant form ofthe invention.

As has been previously mentioned, the invention is particularly welladapted, but not limited, -3, to cleaning devices for dislodging foreignmatter from the perforations of well casing. Accordingly, for thepurpose of illustrating a typical embodiment oi the invention, I haveshown in the accompanying drawings a perforation cleaner .4 positionedwithin a perforated casing or screen C having any suitable type ofperforations, as here conventionally illustrated at P.

'I'he cleaner construction may be regarded generally as comprisingrelatively longitudinally 4 movable body and sleeve portions B and S,the lower portion of the body being in the form of a mandrel M extendingthrough the sleeve S, as will hereinafter more fully appear. Threadablyconnected body or casing sections are indicated 5 at l0, Il and I2 (seeFig. 3), section Il serving as a head or top closure for the chargereceiving or low pressure chamber lla. Coupling I3 is threadablyconnected to section I0 and serves as a means whereby the body may beattached 5 to a suspension element, for example cable I4. Section II,here shown as longitudinally contracted, may be or any desired length;and may be sectional. A 40 it. length gives the charge receiving chamberIIa a capacity ample for most operations.

Section III has a reduced axial bore I5 from which extends a transversepassage I6 controlled by a spring-closed, outwardly opening valvegenerally indicated at I1. The function of this valve is merely to'relieve high pressure in the charge receiving chamber as the tool israised into zones of lower pressure. To facilitate'unloading chamberIla, after the latter has, received a charge and the cleaner is removedfrom the well, there is provided an inwardly opening, springclosed dumprelief valve I3. This valve is fully described in the copendingapplication of W. C. Erwin, et al., on Well bailers, Ser. No. 667,439,filed April 22, 1933, which has matured into Patent No. 2,059,629,granted Nov. 3, 1936. It will sulce here to state that screw plug I3normally closes passageway 23. When chamber IIa is to be unloaded, plugI3 is removed and passageway 26 is then adapted to put the chamber intocommunication with the atmosphere when the lower pressure in the chamber(as created by dumping the uid) is of a value allowing springclosedvalve I3 to open under atmospheric pressure.

Body section I2 has a reduced diameter bore 2I which may be consideredas the inlet opening of chamber IIa, shoulder 22 at the upper end ofbore 2I presenting an upwardly facing seat to take a foot valve 23.Section I2 is also provided with a removable dump door 24, theconstruction and mounting thereof being fully described in the copendingapplication, Ser. No. 667,439. The door is opened by loosening screws 25(which normally press the door inwardly to compress gasket 26 andprovide a fluid-tight seal), rotating the door to clear lugs 21 fromoverhanging lips 23, and then sliding it transversely to clear it fromway 23. It will be understood that the structure thus far describedcomprises no part of the present invention other than as it may beregarded as a typical and convenient type of low pressure chamberconstruction to which the present chamber opening mechanism may beapplied. It is also to be understood that the expression normally closedlow pressure chamber appearing in the claims,. is not intended to limitthe invention to the use of a chamber that is closed at both its upperand lower ends, but rather to dene broadly a chamber that is at leastclosed at one end to normally exclude the well fluid.

Low pressure chamber II a normally is 4closed by a disk 33 clampedbetween the lower end of body section I2 and shoulder 3l within bodysection 32 threadedly connected at 33 with section I2. Disk 36 may bemade of any suitable frangible material, such as glass or other ceramiccomposition, and may conveniently have a downwardly concave shape, asillustrated. It

will sumce to note at this point that disk 30 normally provides afluid-tight bottom closure for the charge receiving chamber IIa, andthat the cleaner is lowered in the well with chamber IIa empty. Afterthe cleaner has been lowered to the depth of the well zone to becleaned, the cleaning operation is then performed by breaking disk 36 toallow a sudden rush of well liquid through the casing perforations P andopenings in sleeve S into the low pressure-chamber IIa,

as will later be more fully explained.

The lower end of section 32 is threadably connected at 35 with thereduced diameter lower tubular section 36 of the body, previouslyreferred to as the mandrel portion M. The lower end of this mandrelsection 36 is closed by a shoe 31, the bottom of which is tapered at 3lto facilitate passing any obstructions that might be encountered whenthe cleaner is being lowered. The sleeve structure S comprises a pair oflongitudinally spaced packers, generally indicated at 39 and 40, whichby engagement with the casing C, confine between them an annular space4I through which suction is applied tothe casing perforations P oppositethe space when the charge receiving chamber is opened, as hereinafterdescribed. As typical, the packers 33 and 40 are shown each to comprisea cup leather or rubber 42 conned within a supporting annulus 43 clampedagainst shoulder 44 on the sleeve tube 45 by spacer sleeves 46, thelatter in turn being held in place by nuts 41. The packers engage thecasing with sumcient tightness to hold the sleeve assembly againstsubstantial vertical movement in the casing during operation of thecleaner, as will later appear. Nuts 43 having rounded end surfaces 46a,are threaded on the upper and lower ends of tube 45.

As best illustrated in the cross section view of Fig. 8. opposite sidesof the mandrel portion 36 of the body are flattened at 56 to form withsleeve 45, longitudinal by-pass passages 5I extending the full length ofthe sleeve. Between passages 5 I, the mandrel 36 has a fairly snug andsubstantially fluid-tight sliding ilt with sleeve 45. As bestillustrated in Fig. '1. a pin 52 terminating in sleeve 45 extendsthrough vertical slots 53 in the mandrel 36. Relative longitudinalmovement between the body and sleeve assembly occurs within the limitsof engagement of nut 43 on the upper end of sleeve 45 with the lower endof body portion 32, see Fig. 1. and the engagement of nut 48 on thebottom of the sleeve with the mandrel shoe 31. as shown in Fig. 5.During such relative longitudinal movement between the mandrel andsleeve, pin 52 travels vertically within slots 53.

The mandrel 36 is chamfered at 55 and 56 at both the upper and lowerextremities of beveled surfaces 50 so that in the uppermost andlowermost positions of the, mandrel relative to the sleeve 48, theby-pass passages 5I will remain in open communication with the interiorof the casing through the openings at 51 and 53, see Figs. l

and 5, formed by the chamfers 55 and 56. Op-

posite sides of the intermediate portion of sleeve 45 between packers 33and 40 have longitudinal slots 60, see Fig. 2, the edges of which arebeveled as indicated at 6I. Through these slots, suction is communicatedto the surrounding space 4I between the packers by way of the mandrelbore 62 and a series of mandrel ports 63 registering with the sleeveslots 63. Some of the uppermost ports 63 may be in registration withslots 66 when the mandrel is in its uppermost position relative to thesleeve, see Figs. 1 and 2, but when the mandrel has been raised to itsuppermost position, as shown in Figs. 4 and 5, all the ports 63 arebrought into register with the slots 60. The

- illustrated construction embodied in the mandrel and sleeve assemblyis more particularly and somewhat more extensively dealt with in acopending application, Ser. No. 22,297 filed May 20, 1935, by James J.Santiago on Well cleaning yievice (G), and reference may be had to thisapplication for further details of this general type of well cleanerconstruction.

In the form of the invention illustrated in Fig. 1, the low pressurechamber closure 36 is opened to admit a well fluid charge by anexplosive element ilred electrically under control of a suitable switchmechanism, the latter being operated by vertical movement of thesuspension means |4. Here the disk 3 8 carries an explosive cap 66 whichmay be embedded in or otherwise carried directly by the disk itself. Thecap is placed in an electric circuit comprising a conductor 61 groundedby contact with shoulder 3|, and an insulated wire 68 connecting with aswitch device generally indicated at 69. Any suitable form of switch maybe used, hence the type illustrated is to be regarded merely as typical.As shown in detail in Fig. 6, the switch 68 comprises an hermeticallysealed body threaded at 1| into and supported by a spider 12 integralwith the cleaner body section 32. The tubular switch body 10 containsone or more batteries 13 placed Within a liner 14 of suitable insulatingmaterial. The insulated conductor wire 68 connects with a terminal 15against the lower end 15a of which the batteries are maintained inengagement by coil spring 16 supported on a metallic switch disk 11placed on the upper insulated end 18 of rod 19. The latter is movablevertically within the body 10 and extends through a packing gland,conventionally illustrated at 80, which prevents the entry of wellliquid to the interior of the switch cylinder. If desired, the tubularbody 16 may contain a suitable non-conductive fluid. The terminal 15extends through a bushing 82 of insulating material, and the connectionbetween Wire 68 and the terminal 15 is insulated by a non-conductivematerial 84 contained within the upper interior of the body 10 abovebushing 82.

A switch actuating mechanism, 'generally indicated at 86, operates toclose the switch and thereby fire the explosive cap 66, by upwardmovement of the suspension means |4 and body B, and as a result ofrelative longitudinal movement between the body and theA sleeve S. Theswitch operating mechanism 86 comprises a rod 81 carrying on its lowerend a looped stirrup 88 through which pin 52 extends. I'he rod andstirrup are supported on spider 89 by a coil spring 90 which normallyholds the rod 81 in the elevated position of Fig. 1, in which positionthe rod engages and holds the switch rod 19 in raised position with thehead 19a engaging the packing gland bushing 86a. Spring 96 thus issufllciently strong to compress spring 16 and keep the switch open untilrod 81 is pulled down to release rod 19 and allow the contact disk 11 tobe moved down, under the influence of spring 16, into engagement withshoulder 10a to close the circuit. Although spring 16 is weaker thanspring 96, the former will be sufficiently strong to` overcome thefrictional resistance to downward movement of rod 19 offered by thepacking gland 80.

In operation, the body B and sleeve S assembly is inserted within thecasing C with the upper portion of the body above section 32, removed.When inserted in the casing, the mandrel M and sleeve S will have therelative position shown in Figs. l and 2, with rod 81 engaging the head19a I taining the low pressure chamber and comprising sections I6, andI2, is next threaded into the upper end of section 32 and the joint at33 taken up to clamp the disk 30 in place. The apparatus is then loweredin the well to the depth of the zone to be cleaned, the packers 39 and40 offering suflicient resistance to downward movement of the sleeve Sto maintain the partsin the relative positions of Figs. 1 and 2.

Pin 52 and the stirrup 88 provide a lost motion connection between thesleeve S and rod 81 in order that if i'or any reason the sleeve shouldtend to drop relative to the mandrel M while the apparatus is beinglowered, the cap 66 will not become prematurely fired to open the lowpressure chamber, before the tool is in proper position for the cleaningoperation. Thus, by virtue of this lost motion connection, sleeve S iscapable of downward movement from the position of Figs. 1 and 2 adistance corresponding to the distance between pin 52 and the lower endoi.' stirrup'88, before rod 81 is pulled down.

When the apparatus has been lowered to'the proper depth, cap 66 is firedto break the disk 30 and open the low pressure chamber by upwardmovement of the suspension means I A and elevation oi' the body B. Asthe body moves upward relative to the sleeve, the lower end of stirrup88 is brought into engagement with pin 52, whereupon rod 81 is heldagainst further upward movement. Since rod 19 is maintained inengagement with the upper end of rod 81 by the action of spring 16,continued elevation of the body causes shoulder 10a to be raised intocontact with disk 11. This contact completes the electric circuit,exploding the cap 66 and breaking disk 36, with the result that the lowpressure chamber ||a is suddenly placed in communication with the bodypassage 92 and mandrel bore 62. Further upward movement of the bodybrings the lower Iend of the mandrel into engagement with the bottom ofsleeve S and the parts into the relative positions of Figs. 4 and 5.

The mandrel ports 63 have thus been brought into registration with slots60 in the sleeve, and byreason of the pressure differential between theformation pressure at the outside of the casing, and the pressure in thecharge receiving chamber l'la, there is induced a sudden ilow of wellfluid through the casing perforationsI P into space 4| between thepackers, and thence through ports 63 into the mandrel bore 62. The wellliquid charge flows upwardly through passage 82, bore 2|, past footvalve 23 into chamber a, and continues to flow into the low pressurechamber until a substantial pressure balance exists. whereupon valve4 23seats to trap the charge in the chamber. The apparatus then is removedfrom the well, and the door 24 removed to dump the charge.

In addition to providing a means for insuring sudden and completeopening of the charge receiving chamber, the explosion of element 66 hasa further advantage in that the combination of the explosive force,followed by the sudden suction effect upon opening the low pressurechamber, is of particular effectiveness in dislodging clogging particlesfrom the casing perforations. When the cap explodes, the expansive forceproduces a sudden downward surge of fluid within the body, out throughports 63 into space 4|, and through the casing perforations, the eect ofwhich is to loosen and displace the clogging particles outwardly in thedirection of the fluid surge. However, this surge is immediatelyfollowed by an equally sudden surge in the opposite direction due to theeffect of the low pressure chamber being put into communication withspace 4|. with the result that the clogging particles, immediately afterthey are loosened by the outward fluid surge, are drawn into theperforations by the oppositely acting impulse.

Fig. 9 shows a variational i'orm of the invention similar in allrespects to the previously described form except as to the means forilring the explosive cap. Here the disk 30a carries an explosive cap 95which is exploded by a spring loaded iiring mechanism, generallyindicated at Il, actuated as a result of upward movement of the body Brelative to the previously described sleeve assembly. Stirrup carryingrod 01', corresponding to rod 01 in the first described form, normallyis supported in a position corresponding to that of Fig. l, by coilspring 91 seating on spider 90 and bearing against a tubular latch 99attached to the upper end of the rod. Latch I operates to releasablyengage and cock the ilring pin |00 which is supported by spring |0| onspider |02.

Upon upward movement of the body B, the parts remain in the positionsshown in Fig. 9 until the lower end of stirrup 08 (referred to inFig. 1) engages pin 02, whereupon continued upward movement of the bodybrings the `spring iinger detents 99a of latch 99 into engagement withthe end enlargement |03 of the ring pin, holding the latter againstupward movement and compressing spring 0|. After spring |0| iscompressed and the iiring pin cocked, further upward movement of thebody releases the enlargement |00 from the latch, causing the firing pinto be projected against the cap 95 to explode the disk and open the lowpressure chamber through inlet 2| into communication with the casingperforations, all in the manner previously explained.

Fig. l0 shows a second variational form of the invention in which thedisk is broken by a projectile nred by an explosive extraneous to thedisk, as distinguished from the previously described forms in which theexplosive is carried directly by the disk. Here the projectile |05inserted within barrel |00 threaded into the upper end of spider I 01,is fired by an explosive cap |08 which is exploded by a iiring mechanism|09 generally similar to the ilring mechanism of Fig. 9. Upon upwardmovement of the body B, latch 99 engages the enlargement |03 on the ringpin |00', causing spring ||0 to be compressed to cock the ilring pin.When released by the latch 99', the ilring pin is projected against thecap |09 and the projectile |05 ired against the disk to break it andopen the low pressure chamber.

I claim:

1. In oil well apparatus of the character described, means iorming anormally closed low pressure chamber, said means including a wallcontaining a well fluid inlet opening, an inlet closure applied directlyto said wall and across said opening, and explosive means adapted to betired to open said closure for the entry of a well iluid charge to thechamber.

2. In oil well apparatus of the character described, means !orming a lowpressure chamber, said means including a wall containing a normallyclosed inlet passage extending therethrough, explosive means adapted tobe ilred to open said passage for the entry of a well iluid charge tothe chamber, and means for firing said explosive means. s

3. In oil well apparatus of the character described, walls forming anormally closed low pressure chamber, explosive means adapted to be redto open said chamber for the entry of a well fluid charge, and meansnormally contained in the apparatus and operating automatically to trapsaid charge in the low pressure chamber.

4. In oil well apparatus of the character described, means forming anormally closed low pressure chamber, said means including a wall at thelower end of said chamber and containing a normally closed, verticallyextending inlet passage extending therethrough, explosive means adaptedto be fired to open said passage for the entry of a well iluid charge tothe chamber, and passage means for ilring said explosive means.

5. In oil well apparatus of the character described, means forming anormally closed low pressure chamber, explosive means adapted to beilred to open said chamber for entry of a well fluid charge, and springactuated means for iiring said explosive means.

6. In oil well apparatus of the character described, a body includingmeans forming a normally closed low pressure chamber, a cable suspendingsaid body in the well, a closure adapted to be opened to admit a wellfluid charge to said chamber, and explosive means adapted to be red toopen said closure.

v'1. In oil well apparatus of the character described, walls forming anormally closed low pressure chamber and containing a well fluid inlet,a frangible closure inserted in said inlet and adapted to be opened toadmit a well fluid charge to said chamber, and explosive means adaptedto be fired to break said closure.

8. In oil well apparatus of the character described, means forming anormally closed low pressure chamber, a closure adapted to be opened toadmit a well fluid charge to said chamber, and explosive means adaptedto be red to open said closure, the last mentioned means comprising anexplosive carried by said closure.

9. In oil well apparatus of the character described, means forming anormally closed low pressure chamber, a closure adapted to be opened toadmit a well fluid charge to said chamber, an explosive carried by saidclosure, and electrically operated means for tiring said explosive toopen the closure.

10. In oil well apparatus of the character described, means iorming anormally closed low pressure chamber, a closure adapted to be opened toadmit a well iluid charge to said chamber, an explosive carried by saidclosure, and means adapted to be projected against said explosive tocause it to ilre and open said closure.

11. In oil well apparatus oi the character described, means forming anormally closed. low pressure chamber, a suspension means on which theapparatus is lowered in the well, explosive means adapted to be ilred toopen said chamber for the entry of a well iluid charge, and meansoperable by movement of said suspension means to tire said explosivemeans.

12. In oil well apparatus oi' the character described, means forming anormally closed low pressure chamber, a. suspension means on which theapparatus is lowered in the well, explosive means adapted to be .red toopen said chamber forthe entry of a well uid charge, and means operableby upward movement of said suspension means to re said explosive means.

13. In well cleaning apparatus adapted to be lowered within a perforatedsection of well tubing, an apertured tubular member adapted to belowered within said perforated well tubing, a pair of spaced tubingengaging packers carried by said member beyond its apertured portion,ex-

plosive means within the apparatus and adapted to be nred to dislodgeclogging particles from the tubing perforations by creating a suddenoutward ow of iiuid through the aperture of said member and through saidperforations, and means for ring said explosive means.

14. In well cleaning apparatus of the character described, a bodyforming a normally closed low pressure chamber, an apertured tubularmember extending below the body and adapted to be lowered within aperforated section of well tubing, the interior of said tubular memberbeing communicable with said chamber, a tubing engaging packer carriedby said member, and explosive means within the apparatus adapted to befired to open said low pressure chamber for the entry of well fluidthrough said perforations and apertured member into the chamber.

15. In well cleaning apparatus of the character described, a bodyforming a normally closed low pressure chamber, an apertured tubularmember extending below the body and adapted to be lowered within aperforated section of well tubing, the interior of said tubular memberbeing communicable with said chamber, a tubing engaging packer carriedby said member, a frangible closure for said chamber at the lower end ofsaid body, and explosive means within the apparatus for breaking saidclosure.

16. In well cleaning apparatus of the character described, a bodyforming a normally closed low pressure chamber, a relatively verticallymovable apertured tubular member extending below the body and adapted tobe lowered within a perforated section of well tubing, the interior ofsaid tubular member being communicable with said chamber, a tubingengaging packer carried by said member, and explosive means within theapparatus adapted to be fired by virtue of relative vertical movementbetween said body and tubular member to open said low pressure chamberfor the entry of well fluid through said perforations and aperturedmember into the chamber.

17. In well cleaning apparatus of the character described, a bodyforming a normally closed low pressure chamber, a relatively verticallymovable apertured tubular member extending below the body and adapted tobe lowered Within a perforated section of well tubing, the interior ofsaid tubular member being communicable with said chamber, a tubingengaging packer carried by said member, a frangible closure for saidchamber, explosive means within the apparatus for breaking said closure,and means operable by relative movement between said body and tubularmember to ilre said explosive means.

18. In well cleaning apparatus adapted to be lowered within a perforatedsection of well tubing, a body containing means operable to dislodgeclogging particles from the tubing perforations by creating a suddenoutward ilow of fluid therethrough, a cable suspending said body in thewell, and means for communicating to the inside of said pe'rforatedsection of tubing an abnormally low pressure to induce a sudden inwardflow of fluid through said perforations immediately after the operationof the rst mentioned means, the last mentioned means being controllableby movement of said cable.

19. In well cleaning apparatus adapted to be lowered within a perforatedsection of well tubing, a suspension means on which the apparatusslowered in the well, means operable by movement of the suspension meansto dislodge clogging particles from the tubing perforations by creatinga sudden outward flow of uid therethrough, means for communicating tothe inside of said perforated section of tubing an abnormally. lowpressure to induce a sudden inward flow of fluid through saidperforations immediately after the operation of the first mentionedmeans, and means confining the communication of said abnormally lowpressure to a portion only of the tubing perforations.

20. In well cleaning apparatus adapted to be lowered within a perforatedsection of well tubing, a tubular member having normally open aperturesadapted to be exposed directly to the casing perforations, meansoperable to dislodge clogging particles from the tubing perforations bycreating a sudden outward now -of uid through said apertures andperforations, means for communicating to the inside of said perforatedsection of tubing an abnormally low pressure to induce a sudden inwardflow of fluid through said perforations immediately after the operationof the ilrst mentioned means, means confining the communication of saidabnormally low pressure to a portion only of the tubing perforations,and means for trapping the uid drawn inwardly through said perforations,for removal to the ground surface.

JOHN GRANT.

